The gene V protein is produced by the f1 bacteriophage which infects E. coli. The protein binds to the viral DNA which is circular and regulates supercoiling. There is a conflict between the previously published structure and the results of 2-D NMR analysis. An improved structure would greatly facilitate the interpretation of the results of studies of point mutations and the determination of their structures through molecular replacement. In 1992, we collected MAD data from crystals in which the methionines had been replaced with selenomethionine. The x-ray structure has now been determined at 2.5w resolution by MAD phasing and has been refined at a resolution of 1.8w with an R-factor of 19.2% using native gene V protein x-ray data. The structure is similar to a previously published x-ray structure for gene V protein, but differs in the alignment of strands of b-structure.